Zeeman-Doppler studies and the rotation evolution of low-mass stars

One of the most important and fundamental properties of low-mass main sequence stars is their rotation period. It is known to correlate with numerous proxies of magnetic activity such as X-ray emission, surface magnetic field strengths and stellar winds. In turn, stellar winds are the main agent of mass- and angular momentum-loss over the main sequence lifetime, causing the rotation period to increase as the star ages. While the mechanisms driving stellar winds are not precisely known, the stellar magnetic field must play an important role.

One way in which the magnetic fields of other stars can be studied is via the Zeeman-Doppler imaging technique. This technique is capable of mapping the large-scale magnetic field topology at stellar surfaces of other stars. To date, ~100 stars have had their surface magnetic fields mapped with this technique providing new insights into how the magnetic fields of cool dwarfs vary with parameters such as stellar mass and rotation. In this talk, I will discuss some of these trends, as well as the implications for stellar rotation evolution along the main sequence.